This invention relates in general to valve assemblies, and, in particular, fuel injectors having a swirl generator. More particularly to high-pressure, direct-injection fuel injectors required to meter accurate and repeatable amounts of fuel for any given injection pulse.
A high-pressure, direct-injection fuel injector is described in the above referenced applications. The fuel injector has a needle reciprocated within a fuel passageway by an armature. The armature is moved by electromagnetic force created by current that flows through a coil assembly located proximate the armature. When the electromagnetic force acts on the armature and operatively connected needle, the armature and needle overcome the load of an armature spring to lift the needle from a seat, which opens the outlet of the fuel injector to begin an injection cycle. To terminate the fuel injection cycle, the electromagnetic force is decayed and held constant until the armature and needle begin to move in the direction of the seat. When the needle fully engages the seat, the outlet of the fuel injection closes, and the injection cycle is completed.
Under certain conditions, however, the needle can rebound (bounce) when it contacts the seat. Because the needle rebounds and fails to fully engage the seat, additional fuel can be injected from the fuel outlet after the desired fuel injection cycle. That is, the valve assembly, which forms the fuel injector, allows for after-flow through the valve assembly when the valve assembly is commanded to terminate a flow cycle. In particular, the fuel injector produces after-injections, which are injections of fuel from the outlet of the fuel injector after the specified injection cycle should have terminated. During particular operative conditions, the needle can rebound numerous times, and create multiple after-injections. These multiple after-injections can reestablish injection fuel flow during the fuel outlet closing procedure. This addition fuel flow deters arcuate fuel injection calibration, which affects subsequent engine calibration. Moreover, the undesired fuel flow minimizes the ability to achieve a linear flow range (LFR) for the fuel injector.